SO I inherited a sprinkler timer that drives me nuts. It is unreliable in the sense that you never know which zone the manual knob will actually effect. For example, I turn the know to zone 1 and change something and that may effect zone 1 or maybe zone 2. This happens with all the zones where you see the digital digital display literally flicker back and forth between reading for the two adjacent options. It actually happens all the way around the knob.
Anyway, is this normal? Can I open and up and adjust something to get to work reliably? If I need to go out and get another, is there one that folks recommend for 6 zones?
Did you "inherit" the timer or a complete irrigation system? If it's just the timer that's bad, I would replace it. Just go to each mfg's site and compare. If it's somewhere in the system, you may need to do some troubleshooting for a short between two zones.
If it's worth doing, it's worth doing right. If you wouldn't put your name on it, it ain't done right!
Is this controller mounted outside? What you describe sounds like what happens to controllers that have been exposed to water or very humid/moist conditions. If thats the case, replace it.
You also mention that you inherited the system, had the controller been "dormant" for a long time without being plugged in? If so its most likely a moisture related failure. We would always leave the controllers plugged in over the winter in the off position in effort to generate some heat with in the cabinet. Not sure if it ever helped but we didn't have to replace any come spring.